London blog Ian Visits has a brilliant feature about a forgotten part of New Cross - an abandoned tube tunnel. Ian writes:

Although South London has but a few tube lines, and they are as scarce as a black cab after midnight, there is still the odd bit of abandoned tunnel even south of the river. One such tunnel is also comparatively modern, having been dug in the early 1970s, then abandoned after just a couple of years.
A short stretch of tube tunnel that leads from nowhere to nowhere, next to the East London Line but not connected to it, this was an experimental tunnel dug as part of the original Fleet Line plans.